This invention relates to electrophysiology catheters, and in particular to a magnetically guidable electrophysiology catheter.
Electrophysiology catheters are elongate medical devices that are introduced into the body and are used for sensing electrical properties of tissues in the body; applying electrical signals to the body for example for cardiac pacing; and/or applying energy to the tissue for ablation. Electrophysiology catheters have a proximal end, a distal end, and two or more electrodes on their distal end. Recently, electrophysiology catheters have been made with electrodes having openings in their distal ends for passage of normal saline solution which cools the surface tissues to prevent blood clotting. These electrodes can be difficult to navigate into optimal contact with the tissues using conventional mechanical pull wires.
The electrophysiology catheter of this invention is particularly adapted for magnetic navigation. The electrophysiology catheter comprises a tube having a proximal end and a distal end, and a lumen therebetween. The tube is preferably comprised of multiple sections of different flexibility, each section being more flexible than its proximal neighbor, so that the flexibility of the catheter increases from the proximal end to the distal end. A first generally hollow electrode member is located at the distal end of the tube. The first electrode has a generally cylindrical sidewall and a dome shaped distal end. There is a second electrode spaced proximally from the first electrode, and in general there are multiple ring electrodes spaced at equal distances proximal to the first electrode. In accordance with the principles of this invention, a magnetically responsive element is positioned at least partially, and preferably substantially entirely, within the hollow electrode member. The magnetically responsive element can be a permanent magnet or a permeable magnet. The magnet is sized and shaped so that it can orient the distal end of the catheter inside the body under the application of a magnetic field from an external source magnet. The magnet is preferably responsive to a magnetic field of 0.1 T, and preferably less. The magnet allows the distal end of the electrophysiology catheter to be oriented in a selected direction with the applied magnetic field, and advanced. Because the magnet is disposed in the hollow electrode, the distal end portion of the catheter remains flexible to facilitate orienting and moving the catheter within the body.
In accordance with one embodiment of the present invention, a temperature sensor, such as a thermistor or thermocouple is mounted in the distal end of the catheter for sensing the temperature at the distal end, for controlling the temperature of the catheter tip during ablation. With this embodiment, the rf energy delivered to the electrode can be adjusted to maintain a pre-selected tip temperature.
In accordance with another embodiment of the present invention, the end electrode is provided with a plurality of outlet openings, the magnetically responsive element has at least one passage therethrough, and a conduit is provided in the lumen to conduct irrigating fluid to the passage in the magnetically responsive element, which conducts the irrigating fluid to the end electrode where the fluid flows out the openings in the end electrode.
In accordance with another embodiment of the present invention, a sleeve is also provided around the tube, creating an annular space for conducting irrigating fluid to a point adjacent the end electrode.
In accordance with still another embodiment of the present invention, the end electrode is provided with a plurality of openings. The magnetically responsive element has a plurality of passages therein for conducting irrigating fluid delivered through a sleeve around the tube to the distal electrode tip, where it is discharged through holes in the tip.